Desert Tortoise

Gopherus agassizii

Like other reptiles, the desert tortoise is cold-blooded. To survive in the desert, the tortoise estivates (remains underground in its burrow)
during the hottest times of the day in the summer and hibernates (sleeps underground in its burrow) through the winter. Tortoises come out in
the spring to eat grasses and wildflowers and drink water from the spring rains (although they obtain most of their water from the plants they eat).
They store water within themselves and use it through the dry months while water is not available. In the spring, they socialize and look for mates.
At other times of the year they are less active above ground.

A Primitive Relic

In America, the term "tortoise" refers to all turtle
species that live primarily on land. According to fossil
records, the desert tortoise, Gopherus agassizii,
is one of four species that have remained virtually
unchanged since the Oligocene Epoch (27-37 million years
ago).

Geographic Range

The desert tortoise occurs today in the Mojave and Sonoran
deserts of southwest Utah, southern Nevada, southeastern
California, and western Arizona.

Longevity

Tortoises are homebodies, spending up to 98% of their time in
burrows, hibernating in the winter and estivating (remaining
inactive) in the summer.

Even when they emerge they never travel far from home, usually
ranging less than one square mile in their lifetime. Sexual
maturity is reached in 15-20 years and their lifespan can often exceed
80 years.

Tortoise Burrows

Burrows are cresent shaped tunnels. The tortoises dome-shaped
shell works as a plug to keep temperature and moisture loss to a
minimum.

A tortoise may excavate and use many burrows during the year.
Most are located at the base of desert shrubs or in wash banks.
Many species of mammals, birds, reptiles, and invertabrates have
been known to share tortoise burrows.

The Clutch

From March to late October, tortoises emerge from their burrows to bask in the
sun, drink, feed and mate. After mating the female deposits her eggs in a hole
she has dug with her hind legs. Clutches range from 1-15 eggs, which she arranges
and covers with soil.

Hatchlings

Baby tortoises hatch from their eggs in 80-130 days and are about one inch in
diameter. The embryos developed into males or females depending on the incubation
temperature of the nest. At approximately 79-87F males are produced and about
87-91F females are produced.

Juvenile Predation

Hatchlings resemble adults and are immediately independent. The number one cause of
newborn mortality is vulnerability to predators due to soft shells, which remain
pliable for the first five years of life. Hatchlings are preyed upon by
coyotes,
ravens,
kit foxes,
badgers,
roadrunners, and
hawks.

The number of predators decreases as the shell hardens.
Hatchlings from only a few eggs out of every hundred actually survive the 7-8 years
it takes to reach adulthood.

Tortoises and Water

Tortoises are able to derive almost all of their water from consuming
plants. In addition, they seek rainwater that collects in natural depressions
or in ones tortoises dig themselves. Adult tortoises can survive a year or more without access to water.

These precious opportunities must last for months. The tortoises large urinary
bladder allows them to store water constituting over 40% of their body weight.
Tortoises can then reabsorb the water within their body as needed.

Tortoise Diet

The Desert tortoise is an herbivore. Grasses form the bulk of its diet,
but it also eats a wide variety of herbs, annual wildflowers, some shrubs, and new growth of
cactuses, as well as their fruit and flowers.

Since droughts are common in the deserts that the tortoise inhabit, they
rely on the erratic years of good rainfall and the ensuing growth of
palatable foods.

Following are a few examples of food that could be included in the diet
of the desert tortoise.

Beavertail CactusOpuntia basilaris
This species is common throughout the desert. Tortoises enjoy eating
the juicy pads and the magenta-colored flowers of this species.

Fluff GrassTridens multicus
This slender, densely tufted grass is prevelant throughout all North American
Deserts. In times of need, it is an important food source for tortoises because
of its abundance.

Desert PlaintainPlantago insularis
The diet of the desert tortoise varies with the season. This tiny annual
flowering plant is an important spring food source for the desert tortoise.

Globe MallowSphaeralcea ambigua
Also know as the "sore-eye" poppy, it was named for the belief that the hairs of the
plant are irritating to the eye. Its bright orange-red blossom is a favorite food source
for the desert tortoise.

Other Animals

The Mojave Desert, despite its sometimes barren and empty appearance, is actually home to over
360 species of animals. It is one of the most diverse ecosystems in North America.

Following is a partial list of other animals that may be seen in tortoise habitats.

Black-chinned HummingbirdArchilius alexandri
This hummingbird is often seen in the spring taking nectar from
wildflowers and occasionally eating small insects.

White-crowned SparrowZonotrichia leucophrys
An attractive sparrow, with distictive white
stripes on its head, can be seen in winter flocks of 5 to 20
foraging for food. They often remain in the same area
for several weeks.

Coachwhip SnakeMasticophis flagellum
The fastest snake in the Mojave, it moves about during the day in search of grasshoppers, lizards
and small rodents. When threatened, it imitates a rattlesnake by curling into a striking
position and vibrating its tail.

Whiptail LizardCnemidopherus spp.
This lizard is aptly named for its whip-like tail which can detach
to aid in its escape from danger. Several species of this lizard
are all females whos eggs require no fertilization. The offspring
are cloned genetic copies of their mothers.

White-tailed Antelope SquirrelAmmosphermophilus leucurus
This bold small animal is often seen sitting upright flicking its expressive tail.
While foraging for seeds and small insects, it makes its presence known by
sounding off with a shrill bark resembling a bird's call in its
clarity.

Desert WoodratNeotoma lepida
This rodent is commonly known as the "pack rat" or "trade rat"
named for collecting any shiny or metallic object it fancies.
Its burrow is easily recognized by the rubbish littered about
the entrance.

TarantulaAphonopelma spp.
These gentle giants are our deserts largest spiders, often having
a leg span of 6 to 7 inches. Despite their fearsome reputation,
they are not dangerous to humans.

Giant Desert Hairy ScorpionHadrurus arizonensis
The southwest's largest scorpion is a secretive, nocturnal animal
that is seldom seen during the day. Its sting, though painful,
is not life threatening.

Cactus WrenCampylorhynchus brunneicapillus
North America's largest wren is often seen scratching around
under ground litter searching for insects, spiders, small lizards
and seeds.

Say's PhoebeSaynoris saya
This annual visitor to the Mojave spends much of its time skillfully
flying about catching insects to eat and to feed its young.